The purpose of this study was to examine relationship between “Internal Working Models” and adaptation in new senior high school students. The survey was conducted among 577 senior high school students. First, a scale to measure students’ “Internal Working Models” was conducted and examined. Results of factor analysis showed that senior high school students’ “Internal Working Models” were composed of 3 factors of 17 items. The reliability of the scale was examined through Cronbach’s α. Second, the relationship between the “Internal Working Models” and adaptation were examined. Results showed that the students’ “Internal Working Models” was related to their adaptation. These results suggested that in case of maladapted senior high school students, psycho-educational intervention is required while paying attention to their “Internal Working Models”